Vehicle information and entertainment systems and consumer entertainment devices may employ sophisticated graphical schemes. A vehicle information and entertainment system may for instance display both safety relevant, such as the vehicle speed and engine temperature, and not safety relevant information, such as video or navigation information at the same time. For example, U.S. Pat. No. 5,784,036 discloses a display device for creating a display image in front of a vehicle's windshield. The display device includes a display controller which controls a display to show safety relevant information, such as vehicle speed and not safety relevant information such as audio system control switches, telephone control switches.
However, a disadvantage of this prior art system is that the display controller may generate a wrong image, for example due to a fault in the hardware or software of the display controller, which may result in a dangerous action of the person looking at the display in case the faulty parts of the image contain safety relevant information.